The present invention relates to an analog voltage memory device which is capable of holding an input voltage signal for a considerably long time by providing an output voltage signal whose magnitude follows the level of the input voltage signal and remains at a desired level thereof.
In the art of analog arithmetic operations and measurements there has been a strong demand for devices capable of holding or storing the analog data for a considerably long time. The conventional devices for this purpose are of the type consisting of a motor and a potentiometer, of the analog memory type consisting of capacitors, magnets and the like or utilizing electrochemical reactions and of the digital type consisting of an analog-to-digital converter, a digital memory and a digital-to-analog converter. However, these conventional devices have their own inherent defects. The analog memory consisting of a motor and a potentiometer has the defects that reliability is low, life is limited because of the mechanical construction and the output is not precisely equal to the input because of mechanical tolerances and that response is slow because of motor control. The analog memories utilizing capacitors, field effect transistors and operational amplifiers have the defect that the memory holding time is too short as a defect of a memory method. The analog memories of the type using a digital-to-analog and an analog-to-digital have the defects that the resolution is rough and the memory is not held because of using a digital memory. That is, when an applied source is not provided, the memory is deleted. The analog memories type consisting of magnets or utilizing electrochemical reactions have defects that the drift of the output rises under the change of peripheral temperature and the level of the output is low.